Silver activated zinc sulfide is almost universally used as the blue color TV primary phosphor. The preparation of this type of phosphor is described in "Introduction to Luminescence of Solids" by H. W. Leverenz, John Wiley & Sons, Inc. 1950.
Up to this time it has been the normal practice for cathode ray tube manufacturers to physically mill the phosphors in the screening vehicle prior to their application to the face plate. This process is somewhat labor intensive since the phosphor slurry has to be pumped from the mill to a container where it is stored until application. It is desirable to have phosphors which could be slurried directly in the storage tanks without first milling the phosphors. This is what is known as stir-in capability.